Several methods and apparatus have been developed for the production of three-dimensional objects or models by irradiation of compositions which crosslink and solidify upon irradiation. U.S. Pat. Nos. 4,041,476 and 4,228,861 to Swainson describe the formation of three-dimensional objects by solidifying each point individually by scanning a volume point by point with intersecting beams of radiation. The Swainson methods are complex and expensive.
U.S. Pat. No. 4,575,330 to Hull describes a method for preparing three-dimensional objects by building up successive thin layers of a solidified photopolymerizable composition. This method has become known as stereolithography. In one embodiment described in the Hull patent, a three-dimensional object is constructed by establishing a thin layer of a photocurable composition on the surface of a platform immersed in a bath of the composition and scanning the layer with a laser beam. The laser controls the X, Y dimension of the model. The Z dimension is controlled by incrementally lowering the platform to greater and greater depths after each successive layer corresponding to a cross-section of the model is polymerized or crosslinked.
Another method for producing three-dimensional objects is described in U.S. Pat. No. 4,940,412 to Blumenthal which discloses a method in which hard copy images having transparent and opaque portions are used as a mask in a photographic process to produce layers which are subsequently stacked and attached to produce a three-dimensional object.
Models prepared previously by the foregoing process methods have been essentially homogeneous in color and texture. It would be desirable to prepare models in which selected elements can be distinctly colored or endowed with a distinct texture, resilience or other tactile characteristic.